Lyme disease is the most prevalent arthropod borne disease in the United States. It is associated with arthritis, carditis, and neurological damage. The incidence of this disease is on the increase, and in some communities it is a major health problem. Borrelia burgdorferi is the causative agent of Lyme disease. Fundamental aspects of its biology, let alone how it causes disease, are yet to be discovered. One special characteristic of B. burgdorferi is its rapid motility and capacity to swim in viscous environments. Motility may be involved in this spirochete's invading and subsequently damaging tissues and organs such as brain, meninges, and eye. Because little is known about how this organism swims, this grant proposes to lay a foundation concerning B. burgdorferi motility. The approach used is multifaceted and includes genetic, microcinematographic, ultrastructural, and biochemical methods. Both mutagen induced and spontaneously occurring motility mutants of B. burgdorferi will be isolated by standard procedures. The main approach is isolating colonies which fail to spread on agarose plates. Revertants to motility will be obtained by plating out the mutants, and picking areas of spreading growth arising from mutant colonies after prolonged incubation. Free swimming and tethered wild-type, mutant, and revertant cells will be analyzed using videomicroscopy, stroboscopically illuminated multiple exposure photography, and high speed cinematography. Several parameters will be monitored, and the results will be analyzed with the aid of a computer. Preliminary multiple exposure photography results indicate that the organism changes its shape during swimming: one translational and two non-translational forms are observed. An hypothesis based on periplasmic flagella rotation is presented which accounts for these forms. The structure of the wild-type, mutants, and revertants will be analyzed by dark-field light microscopy, and transmission and scanning electron microscopy. The periplasma flagella from specific mutants will be morphologically and biochemically characterized. To localize specific mutations, the periplasmaic flagella filament gene from select mutants, revertants, and the wild-type will be cloned and sequenced. The results obtained should enable models and conclusions be drawn concerning mechanisms of B. burgdorferi motility.